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In 1964, workers of the Joint Nuclear Research Institute at Dubna (U.S.S.R.) bombarded plutonium with accelerated
113 to 115 MeV neon ions. By measuring fission tracks in a special glass with a microscope, they detected an isotope that decays by spontaneous fission.
They suggested that this isotope, which had a half-life of 0.3 ± 0.1 s might be rutherfordium-260, produced by the following reaction. Plutonium-242 collides with neon-22 yielding the daughter rutherfordium-260 and four neutrons. Element 104, the first transactinide element, is expected to have chemical properties similar to those of hafnium. It would, for example, form a relatively
volatile compound with chlorine (a tetrachloride). The Soviet scientists have performed experiments aimed at chemical identification, and have
attempted to show that the 0.3-s activity is more volatile than that of the relatively nonvolatile actinide trichlorides. This experiment does not fulfill
the test of chemically separating the new element from all others, but it provides important evidence for evaluation. New data, reportedly issued by
Soviet scientists, have reduced the half-life of the isotope they worked with from 0.3 to 0.15 s. The Dubna scientists suggest the name kurchatovium
and symbol Ku for Element 104, in honor of Igor Vasilevich Kurchatov (1903—1960), late Head of Soviet Nuclear Research. The Dubna Group also
has proposed the name dubnium for Element 104. In 1969, Ghiorso, Nurmia, Harris, K. A. Y. Eskola, and P. L. Eskola of the University of California
at Berkeley reported they had positively identified two, and possibly three, isotopes of Element 104. The group also indicated that after repeated
attempts so far they have been unable to produce isotope 260104 reported by the Dubna groups in 1964. The discoveries at Berkeley were made by
bombarding a target of californium-249 with carbon-12 nuclei of 71 MeV, and carbon-13 nuclei of 69 MeV. The combination of carbon-12 with californium-249 followed by instant emission
of four neutrons produced Element 104-257. This isotope has a half-life of 4 to 5 s, decaying by emitting an alpha particle into nobelium-253, with a half-life
of 105 s. The same reaction, except with the emission of three neutrons, was thought to have produced Element 104-258 with a half-life of about 1/100 s. Element 104-259 is formed by the merging of a carbon-13 nuclei with californium-249, followed by emission of three neutrons. This isotope has a half-life of 3 to 4 s, and decays
by emitting an alpha particle into nobelium-255, which has a half-life of 185 s. Thousands of atoms of Element 104-257 and Eleemnt 104-259 have been detected. The Berkeley
group believe their identification of Element 104-258 was correct. As of January 1995 it was thought that eleven isotopes of Element 104 have been identified.
The Berkeley group proposed for the new element the name rutherfordium (symbol Rf), in honor of Ernest Rutherford, New Zealand physicist. This
name was formally adapted by IUPAC in 1997. 1

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